Implementation of Scaffolds layer for Apple platforms, with related fixes

cocoa/pyproject.toml

@@ -104,6 +104,9 @@ TimeInput = "toga_cocoa.widgets.timeinput:TimeInput"
 Tree = "toga_cocoa.widgets.tree:Tree"
 WebView = "toga_cocoa.widgets.webview:WebView"
 
+# Scaffolds
+Scaffold = "toga_cocoa.scaffolds.base:Scaffold"
+
 # Windows
 MainWindow = "toga_cocoa.window:MainWindow"
 Window = "toga_cocoa.window:Window"

cocoa/src/toga_cocoa/container.py

@@ -8,6 +8,7 @@
     NSLayoutConstraint,
     NSLayoutRelationGreaterThanOrEqual,
     NSView,
+    NSViewController,
 )
 
 #######################################################################################
@@ -131,3 +132,37 @@ def min_height(self):
     @min_height.setter
     def min_height(self, height):
         self._min_height_constraint.constant = height
+
+
+class ControlledContainer(Container):
+    def __init__(
+        self,
+        min_width=100,
+        min_height=100,
+        layout_native=None,
+        on_refresh=None,
+    ):
+        """A container for layouts, wrapped in an NSViewController.
+
+        Creates and enforces minimum size constraints on the container widget.
+        In addition, wrapped in NSViewController to facilitate attachment to various
+        other things like an NSSplitViewItem.
+
+        :param min_width: The minimum width to enforce on the container
+        :param min_height: The minimum height to enforce on the container
+        :param layout_native: The native widget that should be used to provide size
+            hints to the layout. By default, this will usually be the container widget
+            itself; however, for widgets like ScrollContainer where the layout needs to
+            be computed based on a different size to what will be rendered, the source
+            of the size can be different.
+        :param on_refresh: The callback to be notified when this container's layout is
+            refreshed.
+        """
+        super().__init__(
+            min_width=min_width,
+            min_height=min_height,
+            layout_native=layout_native,
+            on_refresh=on_refresh,
+        )
+        self.controller = NSViewController.alloc().init()
+        self.controller.view = self.native

cocoa/src/toga_cocoa/libs/appkit.py

@@ -745,6 +745,10 @@ def NSTextAlignment(alignment):
 NSBezelBorder = 2
 NSGrooveBorder = 3
 
+######################################################################
+# NSViewController.h
+NSViewController = ObjCClass("NSViewController")
+
 ######################################################################
 # NSWindow.h
 NSWindow = ObjCClass("NSWindow")
@@ -834,3 +838,8 @@ class NSDatePickerStyle(IntEnum):
 # NSDatePicker.h
 
 NSDatePicker = ObjCClass("NSDatePicker")
+
+######################################################################
+# NSKeyValueBinding.h
+
+NSTitleBinding = objc_const(appkit, "NSTitleBinding")

cocoa/src/toga_cocoa/scaffolds/base.py

@@ -0,0 +1,181 @@
+from rubicon.objc import SEL, NSObject, objc_method, objc_property
+
+from toga.command import Command, Separator
+from toga_cocoa.container import ControlledContainer
+from toga_cocoa.libs import NSMutableArray, NSToolbar, NSToolbarItem
+
+
+def toolbar_identifier(cmd):
+    return f"Toolbar-{type(cmd).__name__}-{id(cmd)}"
+
+
+class ToolbarDelegate(NSObject):
+    interface = objc_property(object, weak=True)
+    impl = objc_property(object, weak=True)
+
+    @objc_method
+    def toolbarAllowedItemIdentifiers_(self, toolbar):  # pragma: no cover
+        """Determine the list of available toolbar items."""
+        allowed = NSMutableArray.alloc().init()
+        for item in self.impl.toolbar_commands:
+            allowed.addObject_(toolbar_identifier(item))
+        return allowed
+
+    @objc_method
+    def toolbarDefaultItemIdentifiers_(self, toolbar):
+        """Determine the list of toolbar items that will display by default."""
+        default = NSMutableArray.alloc().init()
+        prev_group = None
+        for item in self.impl.toolbar_commands:
+            if (
+                prev_group is not None
+                and item.group != prev_group
+                and not isinstance(item, Separator)
+            ):
+                default.addObject_(toolbar_identifier(prev_group))
+            default.addObject_(toolbar_identifier(item))
+            prev_group = item.group
+
+        return default
+
+    @objc_method
+    def toolbar_itemForItemIdentifier_willBeInsertedIntoToolbar_(
+        self,
+        toolbar,
+        identifier,
+        insert: bool,
+    ):
+        """Create the requested toolbar button."""
+        native = NSToolbarItem.alloc().initWithItemIdentifier_(identifier)
+        try:
+            item = self.impl._toolbar_items[str(identifier)]
+            native.setLabel(item.text)
+            native.setPaletteLabel(item.text)
+            if item.tooltip:
+                native.setToolTip(item.tooltip)
+            if item.icon:
+                native.setImage(item.icon._impl.native)
+
+            item._impl.native.add(native)
+
+            native.setTarget_(self)
+            native.setAction_(SEL("onToolbarButtonPress:"))
+        except KeyError:  # Separator items
+            pass
+
+        return native
+
+    @objc_method
+    def validateToolbarItem_(self, item) -> bool:
+        """Confirm if the toolbar item should be enabled."""
+        try:
+            return self.impl._toolbar_items[str(item.itemIdentifier)].enabled
+        except KeyError:  # pragma: nocover
+            return False
+
+    @objc_method
+    def onToolbarButtonPress_(self, obj) -> None:
+        """Invoke the action tied to the toolbar button."""
+        item = self.impl._toolbar_items[str(obj.itemIdentifier)]
+        item.action()
+
+
+class Scaffold:
+    def __init__(self, interface):
+        self.interface = interface
+        self.container = ControlledContainer(on_refresh=self.content_refreshed)
+        self.root_controller = self.container.controller
+        self._toolbar_items = {}
+        self._toolbar_commands = []
+        self.native_toolbar = None
+        self.toolbar_delegate = ToolbarDelegate.alloc().init()
+        self.toolbar_delegate.impl = self
+        self.toolbar_delegate.interface = self.interface
+
+    def __del__(self):
+        self.purge_toolbar()
+
+    @property
+    def current_container(self):
+        return self.container
+
+    def set_content(self, widget):
+        self.container.content = widget
+
+    @property
+    def title(self):
+        return self.container.controller.title
+
+    @title.setter
+    def title(self, value):
+        self.container.controller.title = value
+
+    def refresh(self):
+        if self.container.content:
+            self.container.content.interface.refresh()
+
+    @property
+    def toolbar_commands(self):
+        return self._toolbar_commands
+
+    # def notify_toolbar_change(self):
+    #     window = self.interface.window
+    #     if window is not None and getattr(window, "_impl", None) is not None:
+    #         window._impl.update_toolbar(self)
+
+    def create_toolbar(self):
+        window = self.interface.window
+        self.purge_toolbar()
+
+        # Shouldn't happen in normal operations, but just in case
+        if window is None:  # pragma: no cover
+            self.native_toolbar = None
+            self._toolbar_commands = []
+            return
+
+        self._toolbar_commands = []
+        if hasattr(window, "toolbar"):
+            self._toolbar_commands.extend(window.toolbar)
+
+        self._toolbar_items = {}
+        for cmd in self._toolbar_commands:
+            if isinstance(cmd, Command):
+                self._toolbar_items[toolbar_identifier(cmd)] = cmd
+
+        if self._toolbar_commands:
+            self.native_toolbar = NSToolbar.alloc().initWithIdentifier(
+                f"Toolbar-{id(self)}"
+            )
+            self.native_toolbar.setDelegate(self.toolbar_delegate)
+        else:
+            self.native_toolbar = None
+
+        if window.content:
+            window.content.refresh()
+
+    def purge_toolbar(self):
+        window = self.interface.window
+
+        # Defensive measure
+        if window is None:  # pragma: no cover
+            return
+
+        while self._toolbar_items:
+            dead_items = []
+            _, cmd = self._toolbar_items.popitem()
+            # Only purge items associated with the current scaffold's
+            # toolbar delegate.  This ensures proper cleanup.
+            for item_native in cmd._impl.native:
+                if (
+                    isinstance(item_native, NSToolbarItem)
+                    and item_native.target == self.toolbar_delegate
+                ):
+                    dead_items.append(item_native)
+
+            for item_native in dead_items:
+                cmd._impl.native.remove(item_native)
+
+    def content_refreshed(self, container):
+        # Apply the minimum size.  This will autoresize the window if needed.
+        self.container.min_width = self.interface.content.layout.min_width
+        self.container.min_height = self.interface.content.layout.min_height

cocoa/src/toga_cocoa/widgets/numberinput.py

@@ -224,7 +224,11 @@ def set_max_value(self, value):
             self.native_stepper.maxValue = float(value)
 
     def set_text_align(self, value):
-        self.native_input.alignment = NSTextAlignment(value)
+        if self.interface.window and self.has_focus():
+            # Drop focus if we're currently focussed, or else alignment setting
+            # will not work properly with Cocoa
+            self.interface.window._impl.native.makeFirstResponder(None)
+        self.native_input.setAlignment(NSTextAlignment(value))
 
     def set_font(self, font):
         self.native_input.font = font._impl.native

cocoa/src/toga_cocoa/widgets/textinput.py

@@ -185,6 +185,10 @@ def set_placeholder(self, value):
         self.native.cell.placeholderString = value
 
     def set_text_align(self, value):
+        if self.interface.window and self.has_focus:
+            # Drop focus if we're currently focussed, or else alignment setting
+            # will not work properly with Cocoa
+            self.interface.window._impl.native.makeFirstResponder(None)
         self.native.alignment = NSTextAlignment(value)
         # The alert label should be on the trailing edge
         if value == RIGHT: